Background: Diffuse axonal injury (DAI), a common cause of neurological sequelae in patients with traumatic brain injury (TBI), is considered one of the most prevalent forms of primary neuronal injury in patients with severe TBI. Cognitive deficits induced by DAI can persist over time, especially following moderate or severe injuries. The aim of the present study was to compare verbal fluency (VF) performance at 6 and 12 months after the trauma in a same group of patients with DAI. Methods: Eighteen patients with moderate to severe DAI and 17 healthy volunteers were enrolled. All DAI participants had sustained a TBI at least 6 months prior to the start of the study, were between 18 and 50 years of age, and had at least 4 years of education. The VF test was administered within an extensive neuropsychological test battery. We evaluated the same patients at 6 months (DAI1 group) and 12 months (DAI2 group) and compared the results of neuropsychological tests with a control group of healthy volunteers who were matched to patients for sex, age, and educational level. Results: In comparison to controls, the DAI1 group produced significantly fewer words. The DAI2 group produced significantly more semantic words than DAI1 (P<0.05) and demonstrated a trend towards the production of more clusters for letter A (P=0.09) and total words generated in a phonemic test (P=0.09). No significant differences were observed between DAI2 and the control group in the total number of words generated in phonetic FAS or semantic fluency scores. Conclusion: The present findings may be useful in the construction of a management plan for long-term TBI rehabilitation that considers the trauma of each patient. Further, our results suggest the VF test is a suitable instrument for the assessment of cognitive difficulties following TBI.